1. Field of the Invention
The present invention relates to a driving torque transmission control apparatus, more particularly, relates to such an apparatus serially between driving force transmission axles to electromechanically control its driving force.
2. Description of the Related Art
Conventionally, it is suggested such an electromagnetically operated clutch apparatus that is serially disposed relative to a propeller shaft to select from a two-wheels driving status to a four-wheels driving status or to control a driving force distribution ratio between front wheels and rear wheels in the four-wheels driving operation Namely, the electro-magnetically operated clutch apparatus is serially disposed between driving force transmission axles to control a driving force transmitted from one of that driving force transmission axles to the other thereof, as described in U.S. patent application Ser. No. 09/014,627 filed on Jan. 28, 1999 by the same Applicant, for example.
In the electromagnetically operated clutch apparatus disclosed above, a bottomed cylindrical first rotating member rotating with one of the driving force transmission axles is relatively rotatably connected around a same center axis with a second rotating member rotating with the other thereof under a case of being disposed in the first rotating member. Between the first and second rotating members, here is provided a frictional engage section to transmit a driving torque from one of the first and second rotating members to the other thereof Further, an electromagnet is rotatably provided relative to the first and second rotating members to control a transmission torque of the frictional engage section. With this configuration, when an exciting current is supplied to the electromagnet through a lead wire, the torque corresponding to an amount of the exciting current is transmitted from one of the first and second rotating members to the other thereof.
However, there is a possibility that a sufficient durability cannot be obtained in the conventional clutch apparatus as described above. It is necessary such that the electromagnet is connected with a non-rotating member for connection of the lead wire with the electromagnet to prevent from its rotation with the first and second rotating members, for example. In such a case, when providing a connection mechanism between a vehicle body or a portion fixed thereto and the electromagnet, a vibration of the vehicle body is transmitted to the electro-magnet, so that the aforementioned clutch apparatus may be decreased in its durability. At an opening portion of the bottomed cylindrical first rotating member, there are farther formed annular clearance inside of the electro-magnet and outside thereof, so that it may be suggested to secure a mask member for covering the annular clearances to the electro-magnet. However, it cannot sufficiently be prevented such an incursion of alien substances by the mask member, whereby the durability may be deteriorated by the incursion. Further, it may be suggested to provide a ring-shaped seal member acceptable for relative rotation in order to seal the annular clearance formed inside of the electromagnet and outside thereof at an opening portion of the bottomed cylindrical first rotating member. In the annular clearance formed outside of the electromagnet, a circumferential speed and the seal member respectively become large in its relative and diameter particularly. Therefore, it has a disadvantage that the durability may. be sufficiently obtained and the seal member and the like becomes high in its cost.